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Diode Laser and Calcium Hydroxide for Elimination of Enterococcus Faecalis in Root Canal

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Original Research Diode Laser and Calcium Hydroxide for Elimination of Enterococcus Faecalis in Root Canal Neda Naghavi1, Armita Rouhani1, Sahar Irani2, Nadia Naghavi3, Elham Banihashemi4 1 Dental Research Center, Mashhad University of Medical Sciences, Mashhad, Iran 2Department of Orthodontics, Faculty of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran 3 Department of Electrical Engineering, Ferdowsi University, Mashhad, Iran 4 General Dentist, Mashhad, Iran Received 5October 2013 and Accepted 12 January 2014 Abstract Introduction: The ultimate goal of endodontic treatment is to eliminate the bacterial infection in the root canal system. While mechanical debridement combined with chemical irrigation removes the bulk of microorganisms, residual bacteria are readily detectable in approximately one-half of teeth just prior to obturation. Laser light can be used to destroy bacteria. This in vitro study was performed to evaluate the effect of diode laser and calcium hydroxide on mono-infected dental canals.Methods: Fifty five single-rooted human premolars were prepared and contaminated with Enterococcus faecalis. After three weeks of incubation, the samples were divided into three experimental groups (n = 15) and two control groups (n = 5). In the first and second groups, the teeth were rinsed for 5 min with either sterile saline or 5.25% NaOCl and irradiated with a 810-nm diode laser at 1.5 W output for 5 × 4s. In the third group, the teeth were rinsed with 5.25% NaOCl and then Ca(OH)2 paste was inserted in the canals for 1 week. Intracanal bacterial sampling was done and the samples were plated to determine the CFU count. Results: 5.25% NaOCl plus laser was as effective as calcium hydroxide and significantly more effective than sterile saline (P>0.05) in elimination of E. faecalis. Complete elimination of E. faecalis was seen only for the one week calcium hydroxide treatment. Conclusion: Combination therapy with NaOCl irrigation and diode laser irradiation can be recommended as an effective treatment option for elimination of E. faecalis from the root canal system. Key words: Antibacterial properties, Calcium hydroxide, Diode laser, Enterococcus faecalis. --------------------------------------------------------- Naghavi N, Rouhani A, Irani S, Naghavi N, Banihashemi E. Diode Laser and Calcium Hydroxide for Elimination of Enterococcus Faecalis in Root Canal. J Dent Mater Tech 2014; 3(2):55-60. Introduction The purpose of root canal therapy is its disinfection and sealing to prevent recurrent infections. Presence or absence of microorganisms in root canals during obturation is the main factor, influencing the outcome of endodontic treatment (1,2). In other words, according to the role of micro-organisms in apical periodontitis, endodontic treatment should focus on removal of microbial colonization from root canal system (through antiseptic procedures) and preventing the entry of new micro-organisms to the root canals (by aseptic techniques) (3). The success of endodontic treatment depends on whether the clinician succeed in achieving these goals or not (4,5). After pulpal infection, bacteria can penetrate into the dentinal tubules as well as periapical tissue. Chemomechanical methods of canal preparation are not able to eradicate bacteria from root canals and dentinal tubules. Approximately 40-60% of microorganisms can survive through chemo-mechanical preparation, which even includes antimicrobial irrigation (6-8). This might be due to their inaccessible location in isthmuses, additional canals and apical region (6). Naghavi et al. JDMT, Volume 3, Number 2, June 2014 55 On the other hand, common irrigators used during endodontic treatment, such as sodium hypochlorite, affect via direct contact to the bacteria. As result,the bacteria which penetrate to the deep layers of dentin can be immune, since irrigator's depth of penetration is limited (9,10). Studies have demonstrated that predictable disinfection of root canal system can only be achieved when inter appointment antimicrobial medicament is placed in root canals (11-13). Researchers tested different laser systems to achieve a more complete disinfection of root canal system and adjacent dentinal tubules and yet there is still controversy about the most powerful laser system in regards to provide a sterilized root canal. High bactericidal effect of Nd-YAG laser and diode laser has been reported in different studies (14).Consequently, due to the bactericidal effect of diode laser and its low cost compared to other endodontic common laser systems, it can be used along with the mechanical debridement procedures. Laser can be transported into canals using fiber optics such as Nd-YAG, argon and diode or with hollow tubes such as CO2 laser and Er-YAG. These different delivery methods can change the potency of similar lasers in canals' sterilization. Use of laser in endodontic treatment has greatly enhanced success rate of treatment and the reason may be due to the laser's ability to penetrate to deeper dentinal layers (15,16). Therefore, the present experimental study was designed to compare the effect of calcium hydroxide with laser diode plus 5.25% sodium hypochlorite and laser diode plus saline in removal of Enterococcus faecalis from root canal system. Materials and Methods Fifty five extracted human single-rooted mandibular premolars were used in current study (three experimental groups of 15 teeth and two control groups of 5 teeth). Exclusion criteria included premolars with more than one root canal or root canal curvature of more than 25, the root surface’s decay and the teeth with calcified canals. After extraction of teeth, their debridement was done by handle instruments and they were kept in normal saline until the experiment day. All crowns were cut from CEJ to achieve a similar root length for all samples (15 mm). In order to determine working length, #15 K-file (Dentsply Maillefer, Ballaigues, Switzerland) was placed in root canals. When the file tip was seen at the apex of the tooth, the working length was recorded by subtracting one millimeter. Afterward, instrumentation was continued with #20 and 25 K-files to remove the pulp tissue and 56 JDMT, Volume 3, Number 2, June 2014 homogenizing the samples. Irrigation was done with 5cc of 5.25% sodium hypochlorite after each file application. Then, all samples were autoclaved at 134 °C for 15 min. At this stage, five teeth were randomly selected and were kept as negative control. Bacterial inoculation Standard suspension of Enterococcus faecalis (ATCC 29212) containing 1.5 × 108 bacteria per ml was prepared and samples were placed into the suspension for 21 days so the bacteria can penetrate fully into the dentinal tubules and form biofilm (17). To meet the needs of growing bacteria, culture medium was replaced every 3 days. After this stage, 5 teeth were randomly kept as positive control. Laser irradiation The remaining 45 teeth were randomly divided into three groups. In all samples instrumentation was done with ProTaper rotary files system (Dentsply, Tulsa Dental, Tulsa, USA), in the way that Sx was the first file to widen the coronal third of the canal, followed by files F2 and F3 to reach the working length. Irrigation and laser irradiation of canals was done according to the divided groups as follows: Group I: The irrigation during preparing canals and in the final stage was done with 5cc sterile saline solution. The diode laser (GmbH ARC Laser, Germany) with a wave length of 810 nm and a power of 1.5W, was then beamed into the canal, in the way that the optical fiber reached up to 1 mm shorter than working length and was rotated with the speed of 2 mm per second, for 5 seconds. This was repeated for four times with a10second interval between. Group II: The irrigation during the preparation was done with 5cc of 5.25% NaOCl followed by a final irrigation with saline. At the end, laser was beamed into the canals similar to the first group. Microbial sampling was performed using size 30 sterile paper points (Aria Dent, Tehran, Iran) placed inside the root canal for 1 min and then transferred to test microtubes containing 1 ml of sterile brain heart infusion broth culture. In order to determine the bacteria within the dentinal tubules, after sampling with paper point, the canals were prepared with sterile Gates Glidden drills # 5 and the samples were taken again (17). The microtubes were vortexed for 30 seconds. 10 ml was removed for counting the number of surviving bacteria on the surface of solid medium and incubated. Cultural plates were evaluated after 24h incubation. Bacterial growth was measured by the CFU/mL counts of E. faecalis. In groups I and II, bacterial sampling was done immediately after irradiation. Group III: The irrigation during the preparation was done with 5cc of 5.25% NaOCl. Calcium hydroxide mixed with sterile saline in equal parts and paste Diode Laser & Calcium Hydroxide inserted into dried canals with the help of lentulo spirals (Dentsply Maillefer, Ballaigues, Switzerland). Cavities were sealed with Cavit (ESPE Dental AG, Seefeld, Germany).A week later, the root canals were irrigated with 5 mL of sterile saline solution and agitated with a size 30 K-file up to the working length in order to remove the intracanal medication. The post-medication samples were collected as previously described. The number of CFU/mL was calculated. In the entire process, sterile instruments were used in order to prevent unwanted contamination of canals. One way ANOVA or Kruskal-Wallis test was used to analyze the data. Results No colonies were found on agar plates in the negative control group to ensure that no contamination of the samples during the experimental period had happened. Extensive growth of bacteria in all samples in the positive control group (CFU = 150000) was observed. Means and standard deviations of CFU in all groups are shown in Table 1.In calcium hydroxide group, no bacterial colonies were observed in any of the samples. The group treated with saline and laser, had zero as minimum number of bacterial colonies and 12000 CFU/ml as maximum, which was a fairly large scatter. In the group disinfected with sodium hypochlorite and laser, the minimum number of bacterial colonies was zero and the maximum was 3000 which was still scattered but it was less than saline –laser group. In general, the number of colonies was significantly different between the tree groups and Mann-Whitney test with Bonferroni correction revealed, difference of colony counts between calcium hydroxide group and hypochlorite-laser group was not statistically significant. But number of colonies in group treated with saline-laser was significantly higher than both other groups. Discussion The success of endodontic treatment depends basically on elimination of the bacteria in root canal system and preventing their re-entry. The remained bacteria after treatment can affect long-term outcome of root canal therapy (3). Despite the proved efficacy of various lasers against microorganisms, studies in regards to laser's antimicrobial ability in root canal system, are controversial. The most of previous studies have shown a fairly high capability of disinfecting dentinal tubules, However complete elimination of endodontic pathogens, especially bacterial species that grows biofilms, has not been achieved (18,19) and further application of these methods with other common antiseptic solutions have been suggested in some studies (20-22). Diode laser has high permeability and low interference with dentin, which allows the laser to be effective on microorganisms that have penetrated into the dentinal tubules(23). Bactericidal capability of the diode lasers on different bacterial species, including Enterococcus faecalis, has been demonstrated by several authors (2427). Bacteria such as Enterococcus faecalis (which is a predominant bacterial species in resistant endodontic infections), are very resistant to endodontic common irrigation solutions (28) and they were isolated from canals with persistent infections and endodontic failures, in several studies (7,29,30). Table1. Mean and standard deviation of CFU/ml and degree of disinfection in the experimental groups, relative to the positive controls Group Number Average Standard Minimum Maximum Test results Disinfection of number of deviation number of number of capability samples colonies colonies colonies (%) Calcium hydroxide 15 .0000 .00000 .00 Saline-laser 15 2012.1429 4252.3553 .00 Hypochlorite-laser 15 206.6667 773.18143 .00 .00 12000.0 3000.00 X2=26.07 P 11.5) (36,37). Since some studies has been shown that the use of laser in canals, irrigated with antiseptic agents or with saline alone are different with each other (20), in this study to further simulate the clinical condition, both types of irrigations were used in combination with laser. In the present study, according tothe significantly lower mean number of bacteria in hypochlorite–laser group compared to saline- laser group (206 vs.2012),it can be concluded the presence of hypochlorite had an important role in increasing the efficiency of diode laser to destroy bacteria. In addition, regards to the concept that efficiency of diode laser would be increased when it's accompanied with other irrigations, de Souza EB et al. (38) in their study stated that the radiation of high power diode laser (wavelength 830 nm and power 3 W) followed by irrigation with 0.5% hypochlorite and17% EDTA-T, will lead to an increased disinfection in deeper layers of root dentin. Results of Kreisler etal.(26) emphasized on the combined use of diode laser and irrigation solutions like NaOCl and H2O2 in endodontic treatments. Moreover, the study of Mehrvarzfar et al. showed that diode laser with use of Biopure MTAD an eradicate Enterococcus faecalis totally from the root canals (20). In the group treated with saline plus laser, the mean bacterial colony was 2012 and according to the colonies of the positive control group (150,000), a 98.6% decrease of bacteria was seen in this group. In this regard, some other studies have suggested that the laser diode is notable to completely remove Enterococcus faecalis (18,24,25). Moritz et al. have shown that complete elimination of bacteria only happens when high power laser is used and this may lead to higher temperature on root surface (27). In Mehrvarzfar study, diode laser with a power of 2 watt was used after irrigation with saline, and it was only 80 percent effective in disinfection of canals (20), while some studies have said that the antibacterial ability of diode 58 JDMT, Volume 3, Number 2, June 2014 laser on dentin blocks with a thickness of 100 micrometers is more than 95 percent (24,25). This difference may be due to the use of dentinal pieces and immediate sampling after laser irradiation, while in Mehrvarzfar experiment, sampling was performed 24 h after laser irradiation and this may provide the time required for regrowth of survived bacteria (20). In the present study, sampling was performed immediately after laser irradiation, and this could cause results to differ with the results of Mehrvarzfar study. Since the analysis revealed that the antibacterial effect of diode laser with parameters used in this study (810 nm, 1.5W) was enhanced in combination with 5.25% sodium hypochlorite, and this group did not have a significant difference with the group treated with calcium hydroxide, for patient’s comfort, clinician can use this strategy in order to disinfect root canal systems as an alternative for the calcium hydroxide medicament in persistent endodontic infections. However, due to the possible harmful effects of lasers on periapical and periodontal tissues, particularly when used in high intensity, further clinical studies should be conducted to understand more fully damage. In addition, in order to understand more about the parameters affecting laser's properties, it is necessary that further studies with other parameters of the laser radiation be conducted. Acknowledgment Present study retrieved from a student thesis (number: 2679). Authors acknowledge Research Council of Mashhad University of Medical Sciences for providing financial support of this research project. References 1. Fabricius L, Dahlen G, sundqvist G, Happonen RP, Möller AJ. Influence of residual bacteria on periapical tissue chemomechanical treatment and root filling of experimentally infected monkey teeth. Eur J Oral Sci 2006;114:278-85. 2. Engström B, Lundberg M. The correlation between positive culture and the prognosis of root canal therapy after pulpectomy. Odontol Revy 1965;16:193-203. 3. Ingle JI, Bakland LK, Baumgartner JC. Ingle’s Endodontics. Hamilton: B.C. Decker Inc, 2008. 4. Sjogren U, Hagglund B, Sudqvist G, Wing K. Factors equilibrium value of MeCpG steps (,+14 deg.) [31,44]. In comparison, methylation has a significantly lower stability cost when happening at major groove positions, such as 211 and 21 base pair from dyad (mutations 9 and 12), where the roll of the nucleosome bound conformation (+10 deg.) is more compatible with the equilibrium geometry of MeCpG steps. The nucleosome destabilizing effect of cytosine methylation increases with the number of methylated cytosines, following the same position dependence as the single methylations. The multiple-methylation case reveals that each major groove meth- PLOS Computational Biology | www.ploscompbiol.org 3 November 2013 | Volume 9 | Issue 11 | e1003354 DNA Methylation and Nucleosome Positioning ylation destabilizes the nucleosome by around 1 kJ/mol (close to the average estimate of 2 kJ/mol obtained for from individual methylation studies), while each minor groove methylation destabilizes it by up to 5 kJ/mol (average free energy as single mutation is around 6 kJ/mol). This energetic position-dependence is the reverse of what was observed in a recent FRET/SAXS study [30]. The differences can be attributed to the use of different ionic conditions and different sequences: a modified Widom-601 sequence of 157 bp, which already contains multiple CpG steps in mixed orientations, and which could assume different positioning due to the introduction of new CpG steps and by effect of the methylation. The analysis of our trajectories reveals a larger root mean square deviation (RMSD) and fluctuation (RMSF; see Figures S2– S3 in Text S1) for the methylated nucleosomes, but failed to detect any systematic change in DNA geometry or in intermolecular DNA-histone energy related to methylation (Fig. S1B, S1C, S4–S6 in Text S1). The hydrophobic effect should favor orientation of the methyl group out from the solvent but this effect alone is not likely to justify the positional dependent stability changes in Figure 2, as the differential solvation of the methyl groups in the bound and unbound states is only in the order of a fraction of a water molecule (Figure S5 in Text S1). We find however, a reasonable correlation between methylation-induced changes in hydrogen bond and stacking interactions of the bases and the change in nucleosome stability (see Figure S6 in Text S1). This finding suggests that methylation-induced nucleosome destabilization is related to the poorer ability of methylated DNA to fit into the required conformation for DNA in a nucleosome. Changes in the elastic deformation energy between methylated and un-methylated DNA correlate with nucleosomal differential binding free energies To further analyze the idea that methylation-induced nucleosome destabilization is connected to a worse fit of methylated DNA into the required nucleosome-bound conformation, we computed the elastic energy of the nucleosomal DNA using a harmonic deformation method [36,37,44]. This method provides a rough estimate of the energy required to deform a DNA fiber to adopt the super helical conformation in the nucleosome (full details in Suppl. Information Text S1). As shown in Figure 2, there is an evident correlation between the increase that methylation produces in the elastic deformation energy (DDE def.) and the free energy variation (DDG bind.) computed from MD/TI calculations. Clearly, methylation increases the stiffness of the CpG step [31], raising the energy cost required to wrap DNA around the histone octamers. This extra energy cost will be smaller in regions of high positive roll (naked DNA MeCpG steps have a higher roll than CpG steps [31]) than in regions of high negative roll. Thus, simple elastic considerations explain why methylation is better tolerated when the DNA faces the histones through the major groove (where positive roll is required) that when it faces histones through the minor groove (where negative roll is required). Nucleosome methylation can give rise to nucleosome repositioning We have established that methylation affects the wrapping of DNA in nucleosomes, but how does this translate into chromatin structure? As noted above, accumulation of minor groove methylations strongly destabilizes the nucleosome, and could trigger nucleosome unfolding, or notable changes in positioning or phasing of DNA around the histone core. While accumulation of methylations might be well tolerated if placed in favorable positions, accumulation in unfavorable positions would destabilize the nucleosome, which might trigger changes in chromatin structure. Chromatin could in fact react in two different ways in response to significant levels of methylation in unfavorable positions: i) the DNA could either detach from the histone core, leading to nucleosome eviction or nucleosome repositioning, or ii) the DNA could rotate around the histone core, changing its phase to place MeCpG steps in favorable positions. Both effects are anticipated to alter DNA accessibility and impact gene expression regulation. The sub-microsecond time scale of our MD trajectories of methylated DNAs bound to nucleosomes is not large enough to capture these effects, but clear trends are visible in cases of multiple mutations occurring in unfavorable positions, where unmethylated and methylated DNA sequences are out of phase by around 28 degrees (Figure S7 in Text S1). Due to this repositioning, large or small, DNA could move and the nucleosome structure could assume a more compact and distorted conformation, as detected by Lee and Lee [29], or a slightly open conformation as found in Jimenez-Useche et al. [30]. Using the harmonic deformation method, we additionally predicted the change in stability induced by cytosine methylation for millions of different nucleosomal DNA sequences. Consistently with our calculations, we used two extreme scenarios to prepare our DNA sequences (see Fig. 3): i) all positions where the minor grooves contact the histone core are occupied by CpG steps, and ii) all positions where the major grooves contact the histone core are occupied by CpG steps. We then computed the elastic energy required to wrap the DNA around the histone proteins in unmethylated and methylated states, and, as expected, observed that methylation disfavors DNA wrapping (Figure 3A). We have rescaled the elastic energy differences with a factor of 0.23 to match the DDG prediction in figure 2B. In agreement with the rest of our results, our analysis confirms that the effect of methylation is position-dependent. In fact, the overall difference between the two extreme methylation scenarios (all-in-minor vs all-in-major) is larger than 60 kJ/mol, the average difference being around 15 kJ/ mol. We have also computed the elastic energy differences for a million sequences with CpG/MeCpG steps positioned at all possible intermediate locations with respect to the position (figure 3B). The large differences between the extreme cases can induce rotations of DNA around the histone core, shifting its phase to allow the placement of the methylated CpG steps facing the histones through the major groove. It is illustrative to compare the magnitude of CpG methylation penalty with sequence dependent differences. Since there are roughly 1.5e88 possible 147 base pairs long sequence combinations (i.e., (4n+4(n/2))/2, n = 147), it is unfeasible to calculate all the possible sequence effects. However, using our elastic model we can provide a range of values based on a reasonably large number of samples. If we consider all possible nucleosomal sequences in the yeast genome (around 12 Mbp), the energy difference between the best and the worst sequence that could form a nucleosome is 0.7 kj/mol per base (a minimum of 1 kJ/mol and maximum of around 1.7 kJ/mol per base, the first best and the last worst sequences are displayed in Table S3 in Text S1). We repeated the same calculation for one million random sequences and we obtained equivalent results. Placing one CpG step every helical turn gives an average energetic difference between minor groove and major groove methylation of 15 kJ/ mol, which translates into ,0.5 kJ/mol per methyl group, 2 kJ/ mol per base for the largest effects. Considering that not all nucleosome base pair steps are likely to be CpG steps, we can conclude that the balance between the destabilization due to CpG methylation and sequence repositioning will depend on the PLOS Computational Biology | www.ploscompbiol.org 4 November 2013 | Volume 9 | Issue 11 | e1003354 DNA Methylation and Nucleosome Positioning Figure 3. Methylated and non-methylated DNA elastic deformation energies. (A) Distribution of deformation energies for 147 bplong random DNA sequences with CpG steps positioned every 10 base steps (one helical turn) in minor (red and dark red) and major (light and dark blue) grooves respectively. The energy values were rescaled by the slope of a best-fit straight line of figure 2, which is 0.23, to por la lectura a través de la lectura de la prensa. La educación en los medios las fuerzas dispersas en función de los soportes mediáticos y orientarse más hacia la educación en medios que al dominio adquiere pleno derecho y entidad en la sección sexta titulada «competencias sociales y cívi- técnico de los aparatos. cas» que indica que «los alum- nos deberán ser capaces de juz- gar y tendrán espíritu crítico, lo que supone ser educados en los las programaciones oficiales, ya que, a lo largo de un medios y tener conciencia de su lugar y de su influencia estudio de los textos, los documentalistas del CLEMI en la sociedad». han podido señalar más de una centena de referencias a la educación de los medios en el seno de disciplinas 4. Un entorno positivo como el francés, la historia, la geografía, las lenguas, Si nos atenemos a las cifras, el panorama de la las artes plásticas : trabajos sobre las portadas de educación en medios es muy positivo. Una gran ope- prensa, reflexiones sobre temas mediáticos, análisis de ración de visibilidad como la «Semana de la prensa y publicidad, análisis de imágenes desde todos los ángu- de los medios en la escuela», coordinada por el CLE- los, reflexión sobre las noticias en los países europeos, MI, confirma año tras año, después de 17 convocato- información y opinión rias, el atractivo que ejerce sobre los profesores y los Esta presencia se constata desde la escuela mater- alumnos. Concebida como una gran operación de nal (2 a 6 años) donde, por ejemplo, se le pregunta a complementariedad entre la escuela y los profesiona- los niños más pequeños si saben diferenciar entre un les de los medios, alrededor del aprendizaje ciudada- periódico, un libro, un catálogo, a través de activida- no de la comunicación mediática, este evento moviliza des sensoriales, si saben para qué sirve un cartel, un durante toda una semana un porcentaje elevado de periódico, un cuaderno, un ordenador si son capa- centros escolares que representan un potencial de 4,3 ces de reconocer y distinguir imágenes de origen y de millones de alumnos (cifras de 2006). Basada en el naturaleza distintas. Podríamos continuar con más voluntariado, la semana permite desarrollar activida- ejemplos en todos los niveles de enseñanza y práctica- des más o menos ambiciosas centradas en la introduc- Páginas 43-48 ción de los medios en la vida de la escuela a través de la instalación de kioscos, organización de debates con profesionales y la confección por parte de los alumnos de documentos difundidos en los medios profesionales. Es la ocasión de dar un empujón a la educación en medios y de disfrutarlos. Los medios –un millar en 2006– se asocian de maneras diversas ofreciendo ejemplares de periódicos, acceso a noticias o a imágenes, proponiendo encuentros, permitiendo intervenir a los jóvenes en sus ondas o en sus columnas Esta operación da luz al trabajo de la educación en medios y moviliza a los diferentes participantes en el proyecto. 5. La formación de los docentes La formación es uno de los pilares principales de la educación en los medios. Su función es indispensable ya que no se trata de una disciplina, sino de una enseñanza que se hace sobre la base del voluntariado y del compromiso personal. Se trata de convencer, de mostrar, de interactuar. En primer lugar es necesario incluirla en la formación continua de los docentes, cuyo volumen se ha incrementado desde 1981 con la aparición de una verdadera política de formación continua de personal. Es difícil dar una imagen completa del volumen y del público, pero si nos atenemos a las cifras del CLEMI, hay más de 24.000 profesores que han asistido y se han involucrado durante 2004-05. 5.1. La formación continua En la mayoría de los casos, los profesores reciben su formación en contextos cercanos a su centro de trabajo, o incluso en este mismo. Después de una política centrada en la oferta que hacían los formadores, se valora más positivamente la demanda por parte del profesorado, ya que sólo así será verdaderamente fructífera. Los cursos de formación se repartieron en varias categorías: desde los formatos más tradicionales (cursos, debates, animaciones), hasta actividades de asesoramiento y de acompañamiento, y por supuesto los coloquios que permiten un trabajo en profundidad ya que van acompañados de expertos investigadores y profesionales. Citemos, por ejemplo en 2005, los coloquios del CLEMI-Toulouse sobre el cine documental o el del CLEMI-Dijon sobre «Políticos y medios: ¿connivencia?». Estos coloquios, que forman parte de un trabajo pedagógico regular, reagrupan a los diferentes participantes regionales y nacionales alrededor de grandes temas de la educación en medios y permiten generar nuevos conocimientos de aproximación y una profundización. Páginas 43-48 Hay otro tipo de formación original que se viene desarrollando desde hace menos tiempo, a través de cursos profesionales, como por ejemplo, en el Festival Internacional de Foto-periodismo «Visa para la imagen», en Perpignan. La formación se consolida en el curso, da acceso a las exposiciones, a las conferencias de profesionales y a los grandes debates, pero añade además propuestas pedagógicas y reflexiones didácticas destinadas a los docentes. Estas nuevas modalidades de formación son también consecuencia del agotamiento de la formación tradicional en las regiones. Los contenidos más frecuentes en formación continua conciernen tanto a los temas más clásicos como a los cambios que se están llevando a cabo en las prácticas mediáticas. Así encontramos distintas tendencias para 2004-05: La imagen desde el ángulo de la producción de imágenes animadas, el análisis de la imagen de la información o las imágenes del J.T. La prensa escrita y el periódico escolar. Internet y la información en línea. Medios y educación de los medios. 5.2 La formación inicial La formación inicial está aun en un grado muy ini- cial. El hecho de que la educación en medios no sea una disciplina impide su presencia en los IUFM (Institutos Universitarios de Formación de Maestros) que dan una prioridad absoluta a la didáctica de las disciplinas. En 2003, alrededor de 1.400 cursillistas sobre un total de 30.000 participaron en un momento u otro de un módulo de educación en medios. Estos módulos se ofrecen en función del interés que ese formador encuentra puntualmente y forman parte a menudo de varias disciplinas: documentación, letras, historia-geografía Estamos aún lejos de una política concertada en este dominio. La optativa «Cine-audiovisual» ha entrado desde hace muy poco tiempo en algunos IUFM destinada a obtener un certificado de enseñanza de la opción audiovisual y cine. Internet tiene cabida también en los cursos de formación inicial, recientemente con la aparición de un certificado informático y de Internet para los docentes, dirigido más a constatar competencias personales que a valorar una aptitud para enseñarlos. 6. ¿Y el futuro? El problema del futuro se plantea una vez más por la irrupción de nuevas técnicas y nuevos soportes. La difusión acelerada de lo digital replantea hoy muchas cuestiones relativas a prácticas mediáticas. Muchos Comunicar, 28, 2007 47 Comunicar, 28, 2007 Enrique Martínez-Salanova '2007 para Comunicar 48 trabajos que llevan el rótulo de la educación en medios solicitan una revisión ya que los conceptos cambian. La metodología elaborada en el marco de la educación en medios parece incluso permitir la inclinación de la sociedad de la información hacia una sociedad del conocimiento, como defiende la UNESCO. En Francia, se necesitaría unir las fuerzas dispersas en función de los soportes mediáticos y orientarse más hacia la educación en medios que al dominio técnico de los aparatos. Los avances recientes en el reconocimiento de estos contenidos y las competencias que supondrían podrían permitirlo. Referencias CLEMI/ACADEMIE DE BORDEAUX (Ed.) (2003): Parcours médias au collège: approches disciplinaires et transdisciplinaires. Aquitaine, Sceren-CRDP. GONNET, J. (2001): Education aux médias. Les controverses fécondes. Paris, Hachette Education/CNDP. SAVINO, J.; MARMIESSE, C. et BENSA, F. (2005): L’éducation aux médias de la maternelle au lycée. Direction de l’Enseignement Scolaire. Paris, Ministère de l’Education Nationale, Sceren/CNDP, Témoigner. BEVORT, E. et FREMONT, P. (2001): Médias, violence et education. Paris, CNDP, Actes et rapports pour l’éducation. – www.clemi.org: fiches pédagogiques, rapports et liens avec les pages régionales/académiques. – www.ac-nancy-metz.fr/cinemav/quai.html: Le site «Quai des images» est dédié à l’enseignement du cinéma et de l’audiovisuel. – www.france5.fr/education: la rubrique «Côté profs» a une entrée «education aux médias». – www.educaunet.org: Programme européen d’éducation aux risques liés à Internet. dResedfeleexliobnuetsacón Páginas 43-48
Diode Laser and Calcium Hydroxide for Elimination of Enterococcus Faecalis in Root Canal
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Diode Laser and Calcium Hydroxide for Elimination of Enterococcus Faecalis in Root Canal

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